GB2301182A

GB2301182A - Method of detecting the stroke movement of a body displaceable in a housing, in particular a valve member of an injection valve

Info

Publication number: GB2301182A
Application number: GB9608914A
Authority: GB
Inventors: Heinz-Arno Marto
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1995-05-17
Filing date: 1996-04-30
Publication date: 1996-11-27
Anticipated expiration: 2016-04-30
Also published as: FR2734358B1; GB2301182B; DE19518072A1; GB9608914D0; FR2734358A1; JPH08313235A; US5654994A

Abstract

The stroke movement of a body displaceable in a housing, in particular a valve member of a fuel injection valve 15, is detected by means of a measuring instrument disposed outside the housing and using X-ray radiation which penetrates the housing at a zone where movement of the body/valve member changes the intensity of the exit beam. An arrangement is described for testing fuel injection valves, particularly valves of the type having dual valve springs to provide initial and main injection quantities. An X-ray source 25 and detector 29 are contained in a shielding enclosure 33 together with a fuel reception structure 21, 23. Signals from the detector 29 and from a pressure sensor 35 are fed to an evaluation and display device 31.

Description

-1DESCRIPTION METHOD FOR THE PURPOSE OF DETECTING THE STROKE MOVEMENT OF A

BODY DISPLACEABLE IN A HOUSING, IN PARTICULAR A VALVE MEMBER OF AN INJECTION VALVE

2301182 Prior Art

The invention relates to a method for the purpose of detecting the stroke movement of a body displaceable in a housing according to the generic type of claim 1.

Methods of this type are necessary for example in order to be able to detect reliably the exact stroke progression of a valve member of an injection valve fitted in particular into the combustion chamber of an internal combustion engine in dependence upon the injection pressure of said valve member during the complete duration of the injection process. in the case of modern internal combustion engines the manner in which the fuel injection process is accentuated by the injection pressure and the valve member stroke is of great importance, since this affects considerably the combustion process in the combustion chamber in particular with regard to the toxic substance emission and the fuel consumption.

The combustion pressure peaks caused by the ignition retardation on autoigniting internal combustion engines can be avoided in this way by means of subdividing the fuel injection process into a preinjection quantity and a main injection quantity. For this type of subdivision of the injection process the opening stroke movement of the -2valve member of the injection valve is divided into two phases, wherein in a preinjection phase firstly only a small injection quantity is released by means of the moving valve member and in a subsequent main injection phase the complete injection quantity is released. In order to create this type of opening stroke movement of the valve member of the injection valve it is known for example from DE-Gbm. 92 059 759 to provide on the injection valve two valve springs which act upon the valve member in the closing direction, of which said valve springs a first valve spring acts continuously upon the valve member and a second valve spring influences the said valve member in the opening direction only after the execution of a prestroke of the valve member. The injection pressure which influences the valve member in the opening direction effects firstly an opening stroke movement (prestroke) of the valve member against the restoring force of the first valve spring, by means of which opening stroke movement the injection cross section which determines the preinjection quantity is controlled. After execution of the prestroke the valve member moves into position at the second valve spring, wherein the pressure build-up of the fuel delivered to injection valve is no longer sufficient to overcome the force of both valve springs, so that the valve member remains for a short period in its stroke position. With the further rise in fuel pressure the second valve spring then also becomes overburdened with pressure, wherein this opening stroke movement of the valve member at this point against the force of both valve springs controls the entire opening cross section on the injection valve, so that the main injection quantity arrives in the combustion chamber of the internal combustion engine by way of the injection orifice.

In order to adapt the injection valve to the requirements of the respective internal -3combustion engine in the best possible way, it is necessary to be able to adjust precisely the duration of the preinjection process and thus the preinjection quantity or the commencement of the main injection process which is dependent directly upon the injection pressure at the injection valve.

To ascertain the time of the commencement of the main injection process in dependence upon the pressure build-up in the injection line which leads to the injection valve it is known for example from DE-OS 41 08 416 to fit into the injection valve a so-called needle movement sensor which detects in a directly mechanical or electromagnetic manner the progression of the stroke movement of the valve member and displays it by way of an indicating instrument. At the same time the pressure in the injection line is ascertained by way of a pressure sensor whose measured values are likewise plotted over time so that an injection pressure value can be associated with the commencement of the second stroke phase (main injection process), which commencement is illustrated as a plateau in the opening stroke progression, which plateau follows on from the preinjection stroke.

The time of the commencement of the main injection process (and likewise when closing the valve) is adapted in this way to the respective requirements in the case of a predetermined injection pressure value by way of the change in the initial bias of the valve springs and in the event of an adjustment of the prestroke path of the valve member.

The known method of measuring has however the disadvantage that the needle movement sensor must be fitted into the injection valve and as a costly component cannot remain there but must be removed, which results in a high assembly cost, so that this method of measuring in particular is not suitable for inspecting series production.

A further known method, in which the time of the commencement of the second opening stroke of the valve member is ascertained only from the progression of the pressure in the injection line (change in the pressure build-up rate), is not sufficiently precise as a result of the very short time periods and dynamic effects, in particular in the case of injection valves which work with high pressures.

Advantages of the invention In contrast thereto, the method in accordance with the invention for the purpose of detecting the stroke movement of a body displaceable in a housing comprising the characterising features of claim 1, which method can be used in a particularly advantageous manner for the detection of the valve member stroke movement of an injection valve and is also applicable for similar measuring procedures on parts which move in a housing, has the advantage that the technique of measuring the stroke progression of the body, in particular of the valve member, can be performed by way of an external measuring device, so that the injection valve does not have to be changed and the measuring technique can be carried out in a simple standardisable manner irrespective of the construction type of the injection valve member (nozzle type). The method in accordance with the invention can be deployed in an advantageous manner for application purposes as well as for inspecting series production, since injection nozzles comprise a standardised external construction so that even different nozzle types can be tested without a modification to the reception device of the measuring device. To this end, the stroke movement of the body or of the valve member stroke of the injection valve is detected in accordance with the invention by means of x-ray radiation which penetrates the housing of the injection valve, wherein a radiation receiver detects the change in the intensity of the radiation and transmits the value to an electronic indicating instrument, in which is plotted over time the change in the intensity of the x-ray radiation which can be associated with a predetermined stroke position of the valve member. An exact valve member stroke value is associated in a simple manner with each point of the pressure progression by means of the synchronised detection of the pressure progression in the injection line of the injection valve. This method of measuring, in which a subsequent comparison with a stored nominal value curve can be carried out, can be automated very simply and this has an advantageous effect on the measurement time period as well as on the accuracy of the measurement.

The injection valve is irradiated for the purpose of detecting the valve member stroke movement in a right-angled manner to the axis of the valve member in a region in which the stroke movement of said valve member effects a change in the intensity of the exiting radiation. This prerequisite is given preferably in regions in which the change in the cross section of the valve member is as large as possible, preferably the conical cross sectional reduction at the injection-side end of the valve member. However, other alternatives are also possible such as for example the use on the -6moved body of different materials whose entrance 1 exit into the x-ray beam change the intensity of the radiation exiting from the housing or into the x-ray beam in the progression of the stroke movement end faces or end face shoulders on the valve member. (SIC) To detect reliably the change in radiation intensity by means of the detector for example a photo multiplier or photonic counter the x-ray beams which exit from the source of radiation are aligned moreover with a narrow limited beam by means of a slot diaphragm, preferably a lead collimator.

In order to be able to prevent safely any x-ray radiation from escaping from the measuring device during the measuring procedure, the device is disposed in a chamber whose walls are constructed out of a radiation proof material and which device is accessible by way of a door (similar to a microwave oven) or the radiation measuring section is closed off towards the outside and is thus inaccessible.

In order to avoid the measuring results being influenced by means of hydraulic characteristics of the injection valve or vibrations and to be able to detect reliably, reproducibly and precisely the change in intensity of the x-ray radiation, the device is mounted in such a way that the pressure which influences the valve member is built up in such a manner that the opening stroke movement of the valve member is greatly retarded with respect to the ratios during the injection process at the internal combustion engine. This is achieved in the exemplified embodiment by virtue of a closed hydraulic system for which reason the injection valve protrudes with its injection orifice into a closed chamber of minimal volume which closed chamber is filled rapidly during the injection procedure by means of the injection valve so that a virtually quasi-static state is created on the valve member owing to the large counterpressure with respect to the operation in the internal combustion engine. Since only the pressure which influences the valve member in the opening direction and the restoring force of the valve springs are decisive for the stroke movement of the valve member in dependence upon the injection pressure prevailing at the valve member, the injection orifices of the injection valve could theoretically also be sealed.

In the exemplified embodiment fuel is used as a pressure medium wherein the pressure build up rate is lowered from approx. 800000 barls in the internal combustion engine to approx. 100 barls at the measuring device. As an alternative to the closed hydraulic system an open system with very large flow rates is also possible which however has the disadvantage of a relatively large high pressure pump.

The closed chamber at the injection valve is designed in an advantageous manner as a closed pressure chamber whose chamber walls consist of a radiation permeable material, preferably aluminium.

The injection pressure is detected in a known manner by means of a pressure sensor which can be designed as an expansion measuring strip or a piezoelectric transmitter and whose measured values are applied over time analogous to the measuring results of the x-ray beam device recorded preferably by means of an oscilloscope, -8so that a pressure value can be associated with the opening and closing stroke progression of the valve member as described above.

The measuring process in accordance with the invention is particularly advantageous for measuring injection valves of internal combustion engines with a stepped valve member stroke progression for a preinjection and main injection (so-called 2 spring nozzle holder combination assembly) but is also suitable for measuring any type of bodies moving in a housing, in particular injection valves comprising an axially displaceable valve member.

Further advantages and advantageous embodiments of the subject matter of the invention are evident from the description, the drawing and the claims.

Drawing An embodiment of a device for the implementation of the method in accordance with the invention for the purpose of detecting the injection pressure at an injection valve in dependence upon the valve member stroke is illustrated in the drawing and explained further hereinunder.

Figure 1 shows a schematic illustration of an exemplified embodiment of the -gmeasuring device and Figures 2 to 4 illustrate the position of the x- ray beam at two types of injection nozzle.

Description of the embodiment

The device illustrated in schematic form in fig 1 for the implementation of the measuring process in accordance with the invention for the purpose of detecting the valve member stroke movement of an injection valve preferably in dependence upon the injection pressure comprises a hydraulic assembly 1 designed as a pressure pump which hydraulic assembly delivers fuel from a storage tank 3 to a hydraulic pressure booster 5 by way of a pressure line 7. In the exemplified embodiment the hydraulic assembly 1 delivers at a pressure between 4 and 150 bar wherein the pressure progression is variable by way of an adjustable valve 9. This valve 9 preferably fitted into the pressure line 7 is designed as a proportional valve, whose through-flow is controlled by virtue of a function generator 11 wherein preferably a pressure build-up rate of approx. 100 barls is set. In the hydraulic pressure booster 5 the fuel delivery pressure is increased at a ratio of 1:5 wherein at the high pressure side an injection line 13 leads from the pressure booster 5 which injection line issues at an injection valve 15 which is to be tested. Furthermore, a so-called manual test stand 17, preferably a manually operated piston pump, is connected to a bypass line 19 which leads from the injection line 13, and by way of this manual testing bench the pressure booster 5 can be charged and discharged.

The injection valve 15 which is to be measured is fitted into a reception device 21 not illustrated in detail wherein the injection side end of the injection valve protrudes in a sealing manner into a pressure chamber 23 whose volume is relatively small with respect to the delivery rate delivered by way of the injection line 13 and which is filled rapidly by the injection valve during the measuring procedure. The reception device 21 and the pressure chamber 23 are manufactured out of a material which is permeable to radiation, preferably aluminium. A radiation source 25 and a reception component 29 are disposed opposite to one another substantially perpendicular to the axis of the injection valve 15 on the external walls of the reception device 21 or the pressure chamber 23. The radiation source 25 is designed as an x-ray tube to which on the outlet side a slot diaphragm 27, preferably a lead collimator, is connected in series by way of which the exiting x-ray radiation is aligned with a narrow limited beam. The reception component 29 (detector) which preferably lies in an axially parallel manner opposite to the x-ray tube 25, is designed as a photo multiplier or photonic counter, whose measured signal is transmitted to an electronic evaluating unit 31 which plots and displays the change in the radiation intensity over time. This evaluating instrument 31 is constructed preferably from a transient recorder or oscilloscope to which a computer, which processes the measured values, is connected. In order to avoid an outward beam emission from the measuring device the injection valve 15, reception device 21, the pressure chamber 23, and the x-ray radiation and reception components 25,29 are disposed in a radiation chamber 33 whose walls consist of a material which absorbs or reflects radiation and which radiation chamber is accessible by way of a door [not illustrated].

Moreover, in order to ascertain the injection pressure progression in the injection line 13, a pressure sensor 35 is fitted in a known manner into said injection line, which pressure sensor can be designed as a DIVIS or piezoelectric transmitter and whose measured values are likewise directed to the electronic display device 31, in which device the measured values are registered over the time and stored.

For the purpose of illustrating exactly how the x-ray radiation penetrates the injection valve 15, two exemplified embodiments of injection valves 15 are shown in Figures 2 to 4. Figure 2 shows a fuel injection valve for internal combustion engines which is designed as a pintle nozzle and comprises a valve member 41 which is axially displaceable in a bore 37 of a valve housing 39 and tapers into a pintle 45 in a conical manner at its lower combustion chamber side end forming a pressure shoulder 43, which pintle protrudes into an injection orifice 47. A conical valve sealing surface 49 is provided at the pintle 45, with which surface the valve member 41 cooperates with a conical valve seat surface 51 at the valve body 39 for the purpose of controlling the injection orifice 47. The bore 37 increases in size in the region of the pressure shoulder 43 to form a pressure chamber 53, in which issues a high pressure duct 55 which is connected to the injection line 13. The closing force is applied on the valve member 41 analogous to DE-Gbm. 92 059 759 by means of two valve springs which are not further illustrated and of which a first valve spring continuously influences the valve member 41 and a second valve spring only moves into position at least indirectly against the said valve member after execution of a predetermined opening stroke path of the valve member 41.

The x-ray beam penetrates the injection valve 15 in the region of the pressure shoulder 43 in a perpendicular manner to the axis of the valve member 41, since the measuring sensitivity of the measuring device is at its greatest in the region where -12the material density of the valve member 41 over its stroke changes to the greatest extent. The second exemplified embodiment of the injection valve 15 illustrated in Figures 3 and 4 is designed as a perforated nozzle which differs substantially to the pintle nozzle illustrated in Figure 2 only in the type of the injection orifice 47. The bore 37 guiding the valve member 41 is designed as a blind hole from whose combustion chamber side closed end leads an injection bore 47. The combustion side end of the bore 37 is designed in a conical manner, wherein the conical sides serve as a valve seat surface 51 and a conical valve sealing surface 49 cooperates at the combustion side end of the valve member 41 with said sides. Also, in this exemplified embodiment the x-ray beam penetrates in the region of the greatest change in the material density of the valve member 41, which region is located at the level of the conical valve sealing surface 49. This type of injection valve 15 is also influenced in the closing direction analogous to Figure 2 by two valve springs, wherein reference is made to the DE-Gbm. 92 059 759 with regard to the known method of operation of this type of injection valves comprising a preinjection and main injection process.

The method in accordance with the invention operates in the following manner.

The hydraulic assembly 1 delivers a pressure medium, preferably fuel, by way of pressure line 7 to the pressure booster 5, which pressure booster in turn delivers at high pressure (up to 700 bar) the medium, preferably fuel, located in its pressure chamber by way of the injection line 13 to the injection valve 15, where the fuel pressure engaging at the valve member 41 effects in a known manner an opening -13stroke movement of the valve member 41 against the restoring force of the valve springs. The fuel exiting from the injection valve 15 at injection orifice 47 fills the pressure chamber 23 extremely rapidly, so that a quasi-static state is created in the closed hydraulic system, which state considerably retards the opening stroke movement of the valve member 41, wherein the pressure build-up in the hydraulic system can be influenced by way of the adjustable valve 9.

The x-ray beam exiting from the x-ray tube 25 is collimated at the slot diaphragm 27 and then illuminates the injection valve in the regions shown in Figures 2 and 4. The valve member stroke causes a change in the intensity of the permeating radiation and this change is proportional to the valve member stroke and is detected by the reception component 29 and passed to the evaluating device 31, where this signal is plotted over time. Simultaneously, the injection pressure in the injection line 13 is detected by way of the pressure sensor 35 and is in turn passed as a signal to the evaluating device 31.

The build up of pressure in the injection line 13 occurs in a linear manner, wherein this continuous rise in pressure results in an extremely uniform valve member stroke comprising an accentuated prestroke plateau between the prestroke movement against the force of the first valve spring and the remaining stroke movement against the force of both valve springs, so that the time of the commencement of the remaining stroke, which corresponds to the commencement of the main injection process, can be ascertained precisely. It is possible by simultaneously ascertaining the injection pressure in the injection line 13 to adjust precisely the injection pressure -14at the commencement of the main injection process.

When using the described measuring device for the purpose of inspecting the correct adjustment of the valve springs (which is decisive for the correct opening stroke progression of the valve member) in the series production of injection valves, the ascertained measured values curve of the injection pressure and the stroke progression is compared with a nominal value curve, so that defective injection valves can be detected immediately.

It is thus possible on a plurality of injection valves in a structurally convenient manner using the method in accordance with the invention with the aid of the x-ray absorption to adjust the temporal progression of the opening stroke movement of the valve member to suit an injection pressure, so that the injection pressure at predetermined stroke positions of the valve member can be ascertained precisely. The method is particularly suitable for use in series production because it can be easily automated.

Claims

-15CLAIMS

1 Method for the purpose of detecting the stroke movement of a body displaceable in a housing by means of a measuring instrument, characterised in that the measuring instrument is disposed outside the housing and the stroke movement of the body is detected by means of x-ray radiation which penetrates the housing, wherein the beam penetration occurs at a point on the moving body at which the stroke movement of the said body causes a change in the intensity of the exiting radiation.

2. Device for the purpose of implementing the method according to claim 1, characterised in that a radiation source for the purpose of beaming the x-ray radiation and a receiver for the purpose of detecting the x-ray radiation which penetrates the housing are provided, wherein the receiver is connected to a device for the purpose of detecting continuously the radiation intensity over time.

3. Use of the method according to claim 1 for the purpose of ascertaining the progression of the stroke movement of a valve member of an injection valve in dependence upon the injection pressure, wherein the stroke movement of the valve member of the injection valve is detected by means of x-ray radiation and comprising a second measuring instrument which detects continuously the pressure affecting the opening stroke movement of the valve member in a pressure medium supply line between a high pressure source and the injection valve.

4. Method according to claim 3, characterised in that the pressure which influences the valve member of the injection valve is built up uniformly and is delayed with respect to an injection pressure progression which occurs in an internal combustion engine when the injection valve is used in the defined manner.

5. Method according to claim 4, characterised in that the rise in pressure at the injection valve occurs during the measuring procedure preferably with 100 barls.

6. Device for the purpose of implementing the method according to claims 2 and 3, characterised in that the radiation source is designed as an x- ray tube at whose beam exit a slot diaphragm is provided which aligns the x-ray radiation with a narrow limited beam and the reception component, for the purpose of receiving the x-ray radiation which penetrates the injection valve, is connected to an electronic instrument for the purpose of detecting and displaying the radiation intensity.

7. Device according to claim 6, characterised in that the injection valve is irradiated in the region of a conical cross sectional reduction at the valve member in a right angled manner to the axis of valve member.

8. Device according to claim 6, characterised in that the free beam measuring section between the exit from the radiation source and the reception component is disposed in a radiation chamber whose chamber walls consist of a radiation proof material.

9. Device according to claim 3 characterised in that the measuring instrument which detects the injection pressure is formed by means of a pressure sensor fitted into the injection line and measured values of the said sensor are detected by an electronic instrument and plotted as a function over time.

10. Device for the purpose of implementing the method according to claim 3 and 4, characterised in that a pressure source designed as a high pressure pump and the injection valve form a closed hydraulic system.

11. Device according to claim 10 characterised in that the injection valve protrudes in a sealing manner with its injection orifice into a closed pressure chamber -17comprising minimal volume whose chamber walls are manufactured from a material which is permeable to x-ray radiation.

12. Device according to claim 11, characterised in that the chamber walls are manufactured from aluminium.

13. Injection valve for the purpose of implementing the method according to claim 3, characterised in that the injection valve comprises a valve member axially displaceable in a bore of a housing which valve member comprises at its one end at least one conical cross sectional reduction and a valve sealing surface with which it cooperates with a valve seat surface at the housing and comprises in the housing at least one injection orifice whose hydraulic connection to the injection line is sealable by means of the sealing surface of the valve member.

14. Injection valve according to claim 13, characterised in that at the injection valve two valve springs, which influence the valve member in the closing direction, are provided, of which a first valve spring influences continuously the valve member and a second valve spring only moves at least indirectly into position at said valve member after execution of a predetermined opening stroke path of the valve member.

15. Use of the device according to claims 3 to 14 for the purpose of detecting a stepped stroke movement of the valve member of the injection valve in dependence upon the pressure which influences the valve member in the opening direction.

16. A method for detecting the stroke movement of a body displaceable in a housing substantially as hereinbefore described with reference to the accompanying drawings.

17. Use of a method for detecting the stroke movement of a body displaceable in a housing for ascertaining the progression of the stroke movement of a value member of an injection valve substantially as hereinbefore described with reference to the accompanying drawings.

18. A device for detecting the stroke movement of a body displaceable in a housing constructed and adapted to operate substantially as herein before described with reference to, and as illustrated in, the accompanying drawings.

19. Use of a device for detecting the stroke movement of a body displaceable in a housing substantially as hereinbefore described with reference to the accompanying drawings.